1. Field of the Invention
The present invention relates generally to a valve system for an internal combustion engine and, more particularly, to a monitoring system that determines the operating condition of the valve system as a function of vibrations created during the operation of the engine.
2. Description of the Related Art
Four cycle internal combustion engines use a valve system that opens and closes the intake and exhaust valve for each cylinder at the appropriate time. Typically, cam shafts with a plurality of cam lobes are used to actuate the movement of the intake and exhaust valves in coordination with the rotation of the crankshaft of the engine.
U.S. Pat. No. 4,638,772, which issued to Burandt on Jan. 27, 1987, describes a valve actuating apparatus for minimizing the need for lash adjustment. A cam unit and a follower at the upper end of the valve stem are configured so that the surfaces between which lash is measured are for all intents and purposes removed or segregated from the surfaces used for effecting valve movement. The modified interaction between the cam and the surface the cam bears against compensates for reduction in valve lash. The segregation is achieved by employing a button having a reduced area engaged by the ramp portions of the cam unit, the ramp portions having a width at least as great as that of the button. In one embodiment, the button is softer than the ramps. Provision is also made for dimensionally correlating the working surface of the cam and follower with the amount of load needed at any given movement to open or close the valve.
U.S. Pat. No. 6,275,765, which issued to Divljakovic et al. on Aug. 14, 2001, discloses a system for providing a prognosis of future engine faults. A method for monitoring an apparatus, such as a marine propulsion system, and determining how various measurements of indicator parameters should be compared to reference magnitudes of those indicator parameters is described. In addition, the method monitors the usage time of the apparatus at various operating conditions to determine whether or not calculated reference magnitudes should be used to determine appropriate and inappropriate power spectral density profiles for various indicator parameters.
U.S. Pat. No. 6,285,947, which issued to Divljakovic et al. on Sep. 4, 2001, discloses a prognostication of future failure of an engine indicator parameter. Power spectral densities are taken at period intervals for preselected indicator parameters and these power spectral density profiles are compared to a reference magnitude of a power spectral density profile for purposes of prognosticated future failures. The power spectral density profile can be for any one of a plurality of indicator profiles, such as an accelerometer output, the output of a pressure sensor, or a voltage output from an ignition system. U.S. Pat. No. 6,745,734, which issued to Pierik on Jun. 8, 2004, describes a variable valve actuating mechanism having torsional lash control spring. A variable valve actuating mechanism includes an output cam pivotally disposed upon an input shaft of an engine. First and second frame members are disposed upon the input shaft on respective sides of the input cam lobe. A first link arm is pivotally coupled at a first end thereof to the first and second frame members. A rocker arm assembly is pivotally coupled at a first end thereof to a second end of the link arm. The rocker arm assembly carries a cam follower that engages an input cam lobe of the input shaft. A biasing means is grounded to the first and second frame members, and biases the cam follower into engagement with the input cam lobe.
U.S. Pat. No. 6,845,312, which issued to Cross et al. on Jan. 18, 2005, discloses a method for detecting engine knock. The method for processing knock related data reduces the memory locations required for the method and also simplifies the processing steps needed to determine a sum, average, and threshold value relating to magnitudes of knock ratios. Inputs from either pressure sensor or accelerometers are filtered and then used to form a ratio between a knock portion of a curve and a reference portion. Sequential magnitudes of the knock ratio are received and analyzed in a manner that reduces required memory locations and improved processing speed.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.